hey...
i use deviantart too and the way i do it have one window open at conceptart.org and another at deviantart.
i right click on my image and go to Properties and in that window there is the address of the image. I copy that address.
Then over here are conceptart i click the IMG button and insert the copied address.

that always works for me but I don't know if there's an easier way.
hope i could help